Field Of The Invention
The present invention relates to a magnetic tape cassette. More particularly, it relates to an improved detecting device for a reader tape in the magnetic tape cassette.
In a magnetic tape cassette, especially a VHS video tape cassette, the difference of light transmittance of a reader tape or a trailer tape from that of a magnetic tape is utilized to detect the top end and the tail end of the magnetic tape. In this case, a magnetic tape having a light transmittance of 0.05 percent or less is usually used. However, certain trouble often occurs in the magnetic tape having a light transmittance of 0.05 percent or more due to fluctuation of the thickness of the magnetic coating film on the magnetic tape or the kind of pigment included in the magnetic coating film. When a video tape operable for a long time and being thin in total thickness is designed, the thickness of the base film should be sufficiently large, so that the thickness of the coated layer is limited. As a result, the light transmittance is too high, thereby preventing the normal operation of the tape.